Vaccinations now protect
against influenza in between 70% and 100% of healthy adults when
the virus and the vaccine are well matched. In the absence of a
match and among the elderly and children, they are fully protective
in 30% to 60% of people.
Vaccines must be redesigned
every year to match the current strain. The antigens in these influenza
viruses undergo genetic alterations (called antigenic drift) over
time, so they are likely to become resistant to a vaccine that worked
in the previous year. Vaccines are then redesigned annually to match
the current strain.
The current flu vaccines
may be slightly less effective in the elderly, the very young, and
patients with certain chronic diseases than in healthy young adults.
People of any age who
are at high risk for serious complications from influenza should
be vaccinated. Such people include those with heart disease, lung
problems, immune deficiencies, diabetes, kidney disease, or chronic
Studies now suggest
that the vaccine is generally safe in patients such as those with
HIV or asthma, and their risk for serious complications from influenza
outweighs any potential adverse effects from the vaccines.
In 2002 the American
Academy of Pediatrics (AAP) and the CDC recommended the vaccination
for all healthy children under two years of age. This recommendation
may vary from year to year depending on the supply of the vaccine.
Children who are receiving
long-term aspirin therapy should also be immunized against the flu
because they are at higher risk for Reye's syndrome, a life-threatening
disease, if they get the flu.
In an interesting study
in Japan it was found that vaccinating children actually helps protect
Newer vaccines contain
very little egg protein, but an allergic reaction still may occur
in people with strong allergies to eggs.
Soreness at the Injection
Site. Almost a third of people who receive the influenza vaccine
develop redness or soreness at the injection site for one or two